How do I switch DHCP from server to DD-WRT-powered router?

Posted on 2009-02-23
Last Modified: 2012-06-27
Hi, first-time poster here.  Hopefully I won't do anything wrong.  I already know this question is gonna be wordy.  ;-)

I am the network admin for a small business - approx. 30 workstations.  Currently we have a Dell PowerEdge 2800 operating as our domain controller (Exchange, Active Directory, DNS, DHCP, etc.), and another 2800 operating as a SQL server.  They both run Windows SBS 2003.  These units have been at the company longer than I have, have had a few upgrades performed by myself, but basically are on their "last legs".  Specifically, it will be the first unit mentioned I'm looking to replace.

We also have one Linksys WRT54G router, modified with DD-WRT firmware, that I installed, and totally love.  This router will be at the heart of my question.

Question is, this server I have, I hate it.  In the past year since I've worked for the company, I've spent countless nights maintaining it.  Not just applying software updates and fixing configuration errors, I've had to replace one of the power supplies, the memory, one of the hard drives, and the tape drive, all have which have failed in the past 12 months.  I'd like to reduce it's necessity to the business, given that eventually this thing is gonna die in a way I can't repair.  I make nightly backups of my Exchange data (the whole system state, in fact), but what I'd like to do is offload as many critical functions from the server to the router as possible.  I'm already in the process of removing all my printers from Active Directory, and setting the workstations to print via standard TCP/IP ports, instead (they're all workgroup-class networked HP printers, why would they need to go through the server?  It's just added overhead, IMHO).  I'd also like to switch DHCP and DNS to go through the router, next.  (note that I've set us up with OpenDNS currently, if that matters)

So how do I disable DHCP & DNS on the server, and switch them to the router?  The router, I think, is the easy part.  DD-WRT is so simple and straight-forward, compared to Server 2003, it's like night & day in my opinion.  I think I can just click on "DHCP server - enable", set the number of users and the range, plug in my preferred DNS servers and be done with it.  But what will be the drawbacks?  I've googled this significantly, and can't find anyone else trying to do what I'm doing.  Is it that unheard of?  Why are people so gung-ho about performing with a complicated and unreliable server, what can easily be done on a hardware level with a good router?  Obviously there's something I'm missing.  Would it somehow royally screw up my domain if I do this?  My ideal solution would be to have everything handled by the router except for the Active Directory logins and Exchange, and my other server still doing SQL, of course.  Does that sound feasible?

Last - should I assign more points to this question?  I just started my account, so guess I only have 125, right?  ;-)
Question by:comptechmike
    LVL 11

    Expert Comment

    All you need to do is disable the DHCP service on the windows box either with the DHCP config tool in administrative tools or under services.msc or you could flat out uninstall the dhcp server under server management or add/remove programs.

    As for drawbacks it really depends on your network. A WRT54G is a pretty cheap router so if you have heavy network traffic/dhcp requests/dns stuff it may cause problems also while I haven't personally used dd-wrt I would imagine you'll lose some logging capabilities.

    Saying that there is no reason you can't try it out (disable not uninstall the dns/dhcp) and configure the router, give it a week and see if you have any headaches. If you still have a job at the end of the week it'll probably be good to go.
    LVL 14

    Accepted Solution

    DHCP is definitely a good candidate for your router.  Unfortunately, DHCP doesn't take too much in the way of resources, so any performance gain on the server will be minimal  (one of those measurable, but not really noticeable, type deals at best)

    You don't even have to uninstall DHCP once you have your router set up.  Just stop the DHCP Server service, and set it to Disabled.

    DNS is not adviseable to move to the router if you have Active Directory in your environment.  If your users log on to the domain, and you move DNS to the router, you will probably see V E R Y long logon times, and access to files on the server may also be negatively impacted.  The router will be perfectly capable of resolving outside(public) DNS records for clients, but AFAIK, it doesn't do Windows DNS.  Clients need Windows DNS to know where their domain controller is, so that when they want to access files, or other computers/servers, they get an authentication token and are granted access rights (or not).  Although it is not DNS that provides these authentication tokens, it is DNS' job to tell clients where to get these authentication tokens (from a domain controller).

    Author Comment


    Ah-ha!  Yes, I've seen this before!  At times when the server was down for whatever reason, I've switched my desktop computer to a static IP & DNS settings, and been able to connect  to the Internet that way - but indeed, the load time is awful.  :-(  Any idea why this is?  Any way to make it not be so slow?
    LVL 4

    Expert Comment

    IMHO you are looking at this from the wrong perspective.  You are trying to address functionality issues when you should be looking at the root of the problem. You have to admit if your server was reliable you would have none of the issues you mentioned.  I would personally spend time making a business case to management for a new server rather than trying to offload it's functions to different pieces of hardware.

    You mentioned the additional TCP overhead for using the server as a print server - if your server is so underpowered that you're implying that printing causes it to slow down then you definitely need a new server, if not then use it for a print server.  Being able to push out printers through Group Policies or even just being able to add a number of printers to a client by left-clicking and hitting "Connect To" is great.

    If you push a lot of the server roles to a DD-WRT router then you will find yourself in the same boat down the road.  If theA lot of services with a a single point of failure that was never designed to leave a home office.  The homebrew firmwares like DD-WRT and Tomato are great, I run Tomato on my home router - but that stays at home, not in a business environment where downtime costs money.

    If you are using Microsoft SBS 2003 (or 2008) the entirety of the server setup is done through easy to read and follow wizard that sets up almost everything for you.  It's not complicated at all.  If you could get a new server, get it setup right the first time with all the services you need, redundant power supplies, etc. your life would be so much easier, you would have more time to work on other projects and management would see savings as they would have much greater uptime and not be spending way too much on older parts trying to keep the server from falling apart.
    LVL 14

    Expert Comment

    Client PCs and other servers need to know where the domain controller(s) are.  If they don't (because Windows DNS is down, for example), then you may experience these long logon times.

    One way to help reduce the chances of this happening is to add a second domain controller (probably not what you wanted to hear).  DHCP, whether Windows or hardware-based, needs to have this second domain controller as a DNS server as well.

    Basically, for access to stuff inside your network, you must have windows DNS running and accessible for smooth operation.

    Author Closing Comment

    Thanks for your tips!  I'm going to try moving DHCP to the router.  It's too bad I can't offload more functions from my crap-tacular server, but I guess I'll have to live with this for now.  ;-)

    BTW - I am working with the accounting dept. to budget for a new server, but you know how it goes in this economy, everybody's pinching pennies...
    LVL 14

    Expert Comment

    I think moving the printer sharing might help some.  Especially if users send big (Mb-size) print jobs to your printers.

    Have you tried to figure out where your bottleneck lies?  It's either CPU, memory, or disk.  CPU and disk are kinda hard/expensive to resolve, but memory is relatively affordable.

    And yes, i agree with the idea of obtaining new hardware if possible.

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